7/28/2019 10.Wiegand, 2007

1/20

7/28/2019 10.Wiegand, 2007

2/20

344 d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 343362

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344

2. Fluoride release of restorative materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344

2.1. Glass-ionomer cements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344

2.2. Resin-modified glass-ionomer cements and polyacid-modified composites . . .. .. . .. .. .. . .. .. . .. .. .. . .. .. . .. .. .. . 345

2.3. Composite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346

2.4. Amalgam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347

3. Factors influencing the release of fluoride from restoratives. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . 347

4. Fluoride recharge of restorative materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348

5. Clinical relevance of fluoride released from restoratives in human saliva and plaque. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349

6. Antimicrobial activity of fluoride-releasing materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349

7. Fluoride uptake of adjacent tooth structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350

8. Influence of fluoride-releasing restoratives on caries development and progression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351

8.1. Influence on demineralization of enamel adjacent to fluoride-releasing restoratives . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351

8.1.1. In vitro studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351

8.1.2. In situ and in vivo studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352

8.2. Influence on demineralization of dentin adjacent to fluoride-releasing restoratives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353

8.2.1. In vitro studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353

8.2.2. In situ studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353

8.3. Clinical studies evaluating secondary caries adjacent to fluoride-releasing restoratives . . . . . . . . . . . . . . . . . . . . . . . . . 353

9. Influence on caries formation of teeth located in interproximal contact to fluoride-releasing restoratives . . . . . . . . . . . . 354

9.1. In vitro and in situ studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354

9.2. Clinical studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354

10. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355

Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355

1. Introduction

Since the observation that secondary caries formation wasrarely associated with fluoride-containing silicate cement

restorations, increasing attention has been focused on the

development of various fluoride-releasing products, to be

used as restorative materials, lining cements, sealants and

orthodontic cements.

Fluoride is well documented as an anticariogenic agent.

A variety of mechanisms are involved in the anticariogenic

effects of fluoride, including the reduction of demineraliza-

tion, the enhancement of remineralization, the interference of

pellicle and plaque formation and the inhibition of microbial

growth and metabolism [14]. Fluoride released from dental

restorative materials is assumed to affect caries formation

through all these mechanisms and may therefore reduce orprevent demineralization and promote remineralization of

dental hard tissues.

Today, there are several fluoride-containing dental restora-

tives available in the market including glass-ionomers, resin-

modified glass-ionomer cements, polyacid-modified com-

posites (compomers), composites and amalgams. Due to

their different matrices and setting mechanisms the prod-

ucts vary in their ability to release fluoride. However, it is

assumed that the antibacterial and cariostatic properties of

restoratives are often associated with the amount of fluoride

released.

This paper aimed to summarize the current status of

fluoride-releasing dental restoratives, their ability to release

and recharge fluoride, their antibacterial activity and car-

iostatic properties. Therefore, original scientific papers and

reviews listed in PubMed or available from peer-reviewed Ger-

manjournals (publishedbetween 1980 and 2004) were includedin the review. Clinical studies concerning the development of

secondary caries at the margin of restorations were taken into

consideration when performed in split-mouth design with an

observation period of at least three years. Papers dealing with

orthodontic or endodontic topics were not included in the

review.

2. Fluoride release of restorative materials

2.1. Glass-ionomer cements

Glass-ionomer cements are composed of fluoride-containing

silicate glass and polyalkenoic acids which are set by anacidbase reaction between the components. During the set-

ting reaction a variety of ionic constituents is released from

the glass, including fluoride. Two mechanisms have been pro-

posed by which fluoride may be released from glass-ionomers

intoan aqueous environment. One mechanism is a short-term

reaction, which involves rapid dissolution from outer surface

into solution (process I), whereas the second is more gradual

and resulted in the sustained diffusion of ions through the

bulk cement (process II) [59]. These processes are presented

by the right-hand first and second terms of the equation:

[F]c = [F]It/(t + t1/2)+ t. The parameter t1/2 is the so-called

half-life of the process I to reach one-half of its maximum

value which is given by F. Parameter t is material depen-

7/28/2019 10.Wiegand, 2007

3/20

d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 343362 345

dent and can be considered as a measure for the driving force

of process II. Forthe mostconventional and the resin-modified

glass-ionomers and some high fluoride-releasing compomers

and composites, the process follows a square root depency

on time suggesting that in some way a concentration gradi-

ent would be responsible for the driving force of the elution

[5,10].

An initial high release from glass-ionomers over the first24h is likelydue to theburst of fluoride released from theglass

particles whenreacting withthe polyalkenoateacid during the

setting reaction.

Karantakis et al. [11] evaluatedthat the highest fluoride dis-

solution occurred especially during the first 4 h after mixing

amounting to 1.61.8g/mm2. Bell et al. [12] showed that the

concentration of fluoride releasedfrom glass-ionomer cement

specimens (1.5mm thick, 6 mm in diameter) into artificial

saliva within 10min after immersion amounted to 1 ppm and

that the cumulative total fluoride in the first 24 h was nearly

15 ppm. In vitro, it is frequently confirmed that the maxi-

mum release occurred during the first 2448 h [1218] rang-

ing from 5 to 155 ppm for different brands of glass-ionomercements (11.5mm thick, 6mm in diameter) [12,14,1619].

Metal-reinforced glass-ionomers seem to release less fluo-

ride than conventional glass-ionomer cements [8,2026]. This

effect may be explainedby the initial lower fluoride content of

these materials due to the replacement by silver or the forma-

tion of silver fluoride which binds the fluoride ions into the

cement preventing leaching of the fluoride [21]. In contrast,

in glass-ionomers containing bioactive glass [27] or casein

phosphopeptideamorphous calcium phosphate [28] fluoride

release seems to be increased comparedto conventionalglass-

ionomers.

After the initial burst, fluoride release slows down and

is followed by a prolonged long-term fluoride release, whichoccurs when the glass dissolves in the acidified water of

the hydrogel matrix [22,29]. Studies have shown that the

cumulative amount of fluoride ions released from glass-

ionomer cements, after a short period of time, is diffusion

controlled and follows a decreasing gradient, which is lin-

ear to the square root of time [10,3032]. Thereby, the ini-

tial high amounts of fluoride rapidly decrease after 2472 h

[11,26,33] and plateaued to a nearly constantlevel within 1020

days [8,15,26,29,34]. After 510 days the cumulative amount

of leached fluoride is about 0.33g/mm2 [11,29,35]. Creanor

et al. [14] found that the concentration of leached fluoride

in deionized water had slowed from 15155 ppm at day 1 to

about 0.94ppm at day 60. After one year, the steady statefluoride release of four different glass-ionomers was approx-

imately 0.57ppm as shown by Perrin et al. [36]. In other in

vitro studies, long-term fluoride release from glass-ionomers

is reported to occur from several months to over three years

[8,14,23,37,38].

In vivo, fluoride concentration of unstimulated saliva

measured immediately after placement of one to six glass-

ionomer restorations increased from approximately 0.04 to

0.81.2 ppm. However, after three weeks the fluoride release

diminished by about 35% and after six weeks for an additional

30% [39]. Nevertheless, the fluoride level in saliva after one

year amounted to 0.3 ppm and was therefore 10 times higher

as baseline values [40].

2.2. Resin-modified glass-ionomer cements and

polyacid-modified composites

Resin-modified glass-ionomer and polyacid-modified com-

posite restoratives have been developed to overcome the

problems of moisture sensitivity and low initial mechanical

strengths typical for conventional glass-ionomers. Polyacid-

modified resin composites (compomers) claim to combine themechanical and esthetic properties of composites with the

fluoride-releasing advantages of conventional glass-ionomer

cements.

Resin-modified glass-ionomers were basically formed

by adding methacrylate components to the polyacrylic

acid, which are polymerizable by light-curing supplement-

ing the fundamental acidbase reaction. Polyacid-modified

resin composites consist of conventional macromonomers

also used in composites, such as Bisphenol-Glycidyl-

dimethacrylate or urethane dimethacrylate, together with

small amounts of acid-functional monomers. The filler glass

is identical to the ion-leachable glass fillers used in conven-

tional glass-ionomer cements but in smaller sizes as knownfromcomposites.Initial setting is performed by light-activated

polymerization which is followed by an acidbase reaction

that arises from sorption of water. Recently, a new category

of hybrid material (giomers) was introduced in the interna-

tional market. Giomers include pre-reacted glass-ionomers to

form a stable phase of glass-ionomer fillers in the restora-

tive. Unlike compomers, fluoro-alumino-silicate glass parti-

cles react with polyacrylic acid prior to inclusion into theresin

matrix.

Resin-modified glass-ionomers were mostly found to have

a potential for releasing fluoride in equivalent amountsas con-

ventional cements [41], but may be affected not only by the

formation of complex fluoride compounds and their interac-tion with polyacrylic acid, but also by the type and amount

of resin used for the photochemical polymerization reaction

[4244]. The kinetics of the cumulative fluoride release of

most resin-modified glass-ionomers are summarized by Ver-

beeck et al. [5] and Xu and Burgess [10] as described above:

[F]c = [F]It/(t + t1/2)+ t.

Fluoride release from different resin-modified glass-

ionomer cements is also highest during the first 24h and

amounted to 535g/cm2 depending on the storage media

[11,15,16,35,45,46]. Mean concentration of fluoride release

from resin-modified glass-ionomer specimens (1.5 mm thick,

6 mm in diameter) into deionizedwater over thefirst 24 h after

setting amounted from 2265ppm for the first 6 h to 320 ppmfor the 1824h period [14]. Daily release rates dropped from

815 ppm (1st day) to 12 ppm (7th day) within 1 week [16,17]

and are stabilized from 10 days [14,33] to 3 weeks [47]. Resin-

modified glass-ionomers continue to release fluoride in small

amountsin vitro (about 12ppm, depending on the specimens

size) for 12.7 years [8,11,37,45,46,48,49].

In contrast to the conventional and resin-modified glass-

ionomers, polyacid-modified composites are mostly shown to

have no initial fluoride burst effect [16,17,48,50], but levels of

fluoride release remain relatively constant over time [17,51].

For the most polyacid-modified composite resins and micro-

filled composite resins, the zero-order kinetics are indicative

of a matrix-controlled elution: [F]c = [F]It/(t + t1/2) +t. Thereby,

7/28/2019 10.Wiegand, 2007

4/20

346 d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 343362

values of are material dependent and can be considered as

measure for the driving force of this process [5,10].

However, short-term fluoride release is slightly increased

during the first few days [17,35,52], but is quite clearly lower

compared to conventional or resin-modified glass-ionomers

[18,33,48,51,5356]. However, thisfinding was not corroborated

by a study ofAttinet al. [57] who found higher fluoride release

for compomers than for glass-ionomer cements. The authorsexplained these differences by the composition of the com-

pomer brands, which exhibited a higher fluoride content and

contained smaller fillers, which might lead to a better reactiv-

ity due to the greater size of the specific surface.

However, the difference between glass-ionomers and

polyacid-modified resin composites during the first phase of

fluoride release could be due to the fact that after curing and

before contact with water the fluoride in polyacid-modified

composites is not free but bound in the filler particles which

are enclosedin thepolymerized matrix. It should be notedthat

in the first phaseof setting, whichis a light-activatedpolymer-

ization, polyacid-modified composites completely behave like

composites. Also, in the second process of fluoride release,dif-fusion of fluoride in a period of up to six months was reported

to be smaller in polyacid-modified resin composites and com-

posites than in glass-ionomers [11,29]. This mechanism is

discussed to be the result from a more tightly bound and/or

less hydrophilic matrix of the composite resin [29]. However,

Asmussen and Peutzfeld [38] found that compomers might

release relatively little fluoride during the first year after set-

ting, but after this time the rate of fluoride release became

equal to that of glass-ionomers.

The main filler fraction in compomers and composites

does differ significantly. When in composites rather inert Ba-

glasses or alike are typically used, the filler glass in a typical

compomer is identical to that of glass-ionomers. Additionallystrontium fluoride or ytterbium trifluoride is added for radio

opacity and may increase fluoride release, too.

With regard to compomers, several authors found differ-

ences in fluoride release in products with different filler sys-

tems. Compomers containing glass fillers and ytterbiumtriflu-

oride are reported to release higher amounts of fluoride than

SrF2-containing products [18,5763].

Daily fluoride release into an aqueous solution from com-

pomers (1.5 mm thick, 6 mm in diameter) declines from

12.4 ppm for the 1st day to 0.170.23ppm after 60 days [18].

With time the initially light cured material takes up water,

and the carboxylic groups of the acidic monomer promote an

acid/base reaction with metal ions of the glass filler. The sub-sequent water sorption leads to ionization of the acid groups.

This reaction takes place at a slow rate and reaches a satu-

ration point after approximately four weeks [64]. Due to this

kinetics, cumulative fluoride release of compomersduring the

first days is expected to be low as compared to conventional

glass-ionomers [17].

Cumulative fluoride release from compomers into deion-

ized water amounted to 0.080.12g/mm2 after 7 days and to

0.390.41g/mm2 after 91 days [29]. After 253 days, weekly flu-

oride release into deionizedwater was reportedto be 0.76 ppm

or rather 1.92g/cm2 [48]. Long-term release of fluoride from

compomers was followed and measured up to three years

[38,48].

Currently, less information is available about fluoride

released from giomers [17,65]. Also, for giomers, no ini-

tial burst effect could be observed. Amounts of fluoride

leached from giomers seem to be slightly higher than from

composites and compomers but lower compared to glass-

ionomers [17,65]. After 24 h, mean fluoride release from spec-

imens (1 mm thick, 6 mm in diameter) into deionized water

amountedto 4.54 ppm anddropped to 0.06 ppm perday withinone week [17].

2.3. Composite

Resin composites may contain fluoride in a variety of forms,

such as inorganic salts, leachable glasses or organic fluoride.

Thereby, not only the amount of fluoride but type and particle

size of the fluoridated filler, the type of resin, silane treat-

ment and porosity might be important factors contributing

to fluoride release [10,6669]. Moreover, the fluoride release

increased with the hydrophilicity and the acid character of

the polymer matrix [38].

Three different approaches for the development offluoride-releasing composites have been reported including

the addition of water-soluble salts such as NaF or SnF2,

fluoride-releasing filler systems or matrix bound fluoride (for

review see [67]).

Incorporation of inorganic fluoride has resulted in

increased fluoride release, but leads to voids in the matrix as

the fluoride leaches out of the material. Dispersion of leach-

able glass or soluble fluoride salts into the polymer matrix

allows for a water-soluble diffusion of fluoride from the com-

posite resin in the local environment. Most of the fluoride

is already released during the setting reaction, followed by a

smaller amount of long-term fluoride release.

Mainly twofillertypes can be distinguished, sparingly solu-ble compounds, such as strontium fluoride (SrF2) or ytterbium

trifluoride (YbF3) and leachable glass fillers [10,59,67]. The

composites in which the radioopaque fluoridated filler YbF3was used most likely release fluoride by means of an exchange

reaction. Water diffusion into the composite causes fluoride

release from the particles followed by a diffusion gradient

driven movement into the environmental solution (water and

saliva). As mentioned before, fluoride silicate fillers in glass-

ionomers and resin-modified glass-ionomersare moresoluble

and thus release more fluoride especially when reacting with

the polyacrylic acid. Finally, organic fluoride components have

been added to the matrix to increase the fluoride release.

Matrix bound fluoridesare available such as acrylic-amine-HF-salts, methacryloyl acid-fluoride and acrylic-amine-BF3 [70].

Fluoride levels leached from composites are mostly much

lower compared to levels released from conventional or resin-

modified glass-ionomers and also somewhat lower as com-

pared to polyacid-modified composites [11,18,29,37,38,71,72].

Initial fluoride release into deionized water within 24h

amounted to 0.042.7ppm for different composite brands

(1.5 mm thick, 6 mm in diameter), but decreased to 0.022ppm

within 3060 days [16,18]. Weekly release from specimens

(1 mm thick, 15 mm in diameter) is also reported to decrease

from 34 to 12ppm within a few weeks [73]. Cumulative

fluoride-releasing rates in artificial saliva, lactic acid or deion-

ized water amounted to less than 0.5 g/mm2 during 90120

7/28/2019 10.Wiegand, 2007

5/20

d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 343362 347

days [11,29]. Long-term release of different commercial and

experimental resin composites is reported to last for up to five

years [66,7476].

It could be shown that experimental highly fluori-

dated composites and an ion-releasing composite (Ariston)

released higher amounts of fluoride than conventional flu-

oridated composites [16,66,77]. While most commercially

available composites exhibited a fluoride release which isapproximately proportional to the logarithm of time or to

t1/2 [66,73], an experimental high-fluoridated compositeshowed a linear fluoride release, which is proportional to t

[66,78].

The high fluoride release of these experimental or high-

fluoridated composites is discussed to be a result of a high

fluoride content (F-Al-silicate and YbF3) combined with high

watersolubilityof the filler, high water uptake anda highly dif-

fusible polymer matrix [10,16,66], the latter two reasons being

the cause for clinical failures as shown by Braun et al. [79] and

Merte et al. [80].

2.4. Amalgam

Several studies investigated fluoride levels released from

amalgam [23,8184]. Storage of conventional amalgam class

V restorations in deionized water revealed fluoride values

of less than 0.02 ppm within four weeks [84] and less than

0.08ppm one year after insertion [83]. Cumulative fluoride

content after placement of amalgam specimens (1.6 mm

thick, 15.2mm in diameter) in artificial saliva amounted to

less than 0.1g/mm2 within seven weeks [82]. These results

are also confirmed for fluoride-containing amalgam samples

(2mm2 mm12mm) [85]. The initial release of fluoride intohydroxyapatite decreased from 0.33 to 0.009g/mg withinone

week [85].In summary, fluoride release from different fluoridated

restorative materials may last for a long period. However, after

a higher initial release, fluoride release from these materials

may drop to very low levels.

3. Factors influencing the release offluoride from restoratives

The elution of fluoride is a complex process. It can be affected

by several intrinsic variables, such as formulation and fillers

[27,28,31,42,86,87]. It is also influenced by experimental fac-

tors, i.e. storage media, frequency of change of the storagesolution, composition and pH-value of saliva, plaque and

pellicle formation [9,12,21,32,35,52,8894]. It was shown that

the powderliquid ratio of two-phase-systems, mixing proce-

dure, curing time and the amount of exposed area as well

as the different storage media affected the fluoride release

[21,29,32,36,92,9598]. In vitro, fluoride release was dependent

on exposed surface area and not on sample weight [32]. Radi-

antheat applied to glass-ionomers at different intensities and

for different time intervals using a high-intensity fibreoptic

quartz tungsten halogen light source had no effect of fluoride

release [99].

Several laboratory studies investigated the quantity of

fluoride released into water, artificial saliva or acidic solu-

tions. Kinetic findings demonstrated that the patterns of flu-

oride release from conventional and resin-modified glass-

ionomers as well as compomeres and composites in dif-

ferent storage media were similar. However, the amount of

daily and accumulated fluoride release of these materials

is different as mentioned above [11]. On long term, com-

posites have mostly shown to release lower amounts of

fluoride compared to glass-ionomer, resin modified glass-ionomer and compomer [11,23,29,38]. In general, the highest

release is found in acidic and demineralizingremineralizing

regimes andthe lowest in saliva [11,35,52,53,57,71,94,100102].

Demineralizingremineralizing regimes are chosen for sim-

ulating the pH-cycling that occurs during caries attack. The

increasing amount of fluoride in acidic media could be

explained by the fact that a decrease in pH increases the dis-

solution of the material leading to a higher fluoride level in

the acidic immersion [11,52,63,94,102,103]. Thereby, the pro-

portion of free (uncomplexed) fluoride to bound (complexed)

fluoride was lower under acidic than under neutral condi-

tions [94,103]. Artificial saliva tends to decrease the amount

of leached fluoride to 1725% of that found in water [12]. Thisobservation might be explained by the fact that the diffusion

gradient between the restorative material and ion-enriched

saliva is lower as compared to the gradient between the

restorative and distilled water. Moreover, it is suggested that

components from saliva form a pellicle on the surface of the

restorative material that impedes ion release [8,12,101,104].

Bell et al. [12] showed that salivary depositson glass-ionomers

formed within the first 10 min after immersion into saliva

caused a retarding effect on fluoride release. Moreover, Arends

et al. [67] found that the presence of a pellicle reduced the

fluoride-releasing rate of a fluoridated composite by about

1520%.

Nevertheless, in human saliva fluoride rates may beincreased due to the activity of salivary enzymes. It was

demonstrated that fluoride release from resin-modified glass-

ionomers and compomers may be increased in esterase-

containing artificial saliva compared to artificial saliva free

of enzymes [105107]. It was also discussed that plaque-

associated organic acids or salivary hydrolases may increase

initial fluoride release in vivo [107]. The clinical relevance of

fluoride released in human saliva or plaque will be discussed

separately.

It should be noted that covering of the materials with

adhesives or bonding agents may influence the short- and

long-term release of components of dental filling materials.

Immediateapplicationof a surface coating agent might alsobeperformed to protect glass-ionomers from moisture contam-

ination and dehydration during initial setting. Even though

fluoride-containing dental adhesives are able to release flu-

oride in a range from 4 to 30 g/cm2 during eight weeks

[46,108,109], adhesive coating of the material surface signif-

icantly reduces the amount of fluoride leached from glass-

ionomers and compomers [15,62,90,100,110,111]. In vitro, flu-

oride leached from filling materials coated with an adhesive

was reduced by a factor 1.54 [62,112,113].

Neither bleaching nor brushing of restorative materials

increased the amount of fluoride release. Home-bleaching or

in-office bleaching agents containing 10 or 35% carbamide

peroxide have shown to be ineffective in increasing the

7/28/2019 10.Wiegand, 2007

6/20

348 d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 343362

release of fluoride from conventional and resin-modified

glass-ionomers as well as composites [114].

Removal of the outermost layer of compomers by air-

polishing or finishing maylead to an increased fluoride release

[90,115]. This pattern was explained by the fact that air-

polishing removes the outer surface of a water-immersed

specimen which leads to exposition of deeper zones of the

material not depleted of fluoride. However, simulation of oralhygiene behavior by brushing of a polyacid-modified compos-

ite with a fluoride-free dentifrice didnot maintain the initially

high level of fluoride release for a longer period of time com-

pared to unbrushed samples [60].

4. Fluoride recharge of restorative materials

The cariostatic action associated with fluoride-releasing

materials is usually attributed to a sustained release of fluo-

ride. Due to the fact that fluoride levels leached from fluoride-

containing filling materials decreased over time (which is

significant for glass-ionomers and resin modified glass-ionomers), the recharging of restoratives with fluoride has

been suggested to maintain a continuously increased level of

fluoride release. The ability of a restorative to act as a fluoride

reservoir is mainly dependent on the type and permeability of

filling material, on the frequency of fluoride exposure and on

the kind and concentration of the fluoridating agent [116,117].

A review of previous in vitro and in situ studies showed that

various methods of aging (deionized water, distilled water and

artificial/human saliva), periods of aging (days to months) and

methods of fluoride recharge may also actas contributory fac-

tors [52,117122].

Fluoride release after application of fluoridated agents may

occur partly by washout of fluoride ions that are retained onthe surface or inthe poresof therestorative. Surface boundflu-

oride might be more easily detached during an acidic attack,

such as erosions. Also, free fluoride incorporated into the

matrix might be washed out [47].

Glass-ionomers are mostly found to have significantly bet-

ter capability to act as a fluoride reservoir than composite

resin-based materials [18,52,72,77]. This fact can be explained

by the loosely bound water and the solutes in the porosi-

ties in the glass-ionomer, which may be exchanged with an

external medium by passive diffusion [10,123]. The absorp-

tion and re-release of fluoride might be determined by the

permeability of the material. Thus, a completely permeable

substance could absorb the ions deep into its bulk, while arelatively impermeable material can only absorb fluoride into

the immediate subsurface [116]. Therefore, the slight increase

of fluoride release from resin-based restoratives after expo-

sure to exogenous fluoride is discussed to be most probably

because of surface-retained fluoride [18]. In general, materi-

als with higher initial fluoride release have higher recharge

capability [10,16,124,125]. However, fluoride release from aged

and refluoridated specimens mostly did not reach the initial

fluoride release of the material [16,18,126].

In vitro, comparison of fluoride leached from one-

time refluoridated conventional and resin-modified glass-

ionomers, ion-releasing composite as well as flowable

and packable compomers and composites showed an

increased fluoride release for 24 h followed by a rapid return

to near pre-exposure levels already within several days

[16,18,120,126128]. Three months after single application of

1.23% APF to aged restorative materials, fluoride release of

glass-ionomers and compomers was even lower than imme-

diately before gel application [125].

Refluoridation of glass-ionomers, compomers and com-

posites with a 500 ppm F solution 13 times over a two-yearperiod revealed different capacities among the materials with

respect to absorbtion and release of fluoride. After 720 days,

glass-ionomer-based materials displayed a far better poten-

tial to re-release fluoride (312gF/cm2, 1 h post-recharge)

than composites (0.20.3gF/cm2, 1 h post-recharge) and per-

formed somewhat better than compomers (3.65gF/cm2, 1 h

post-recharge) [72].

In the oral environment, dental restorations are frequently

exposed to exogenous sources of fluoride, such as fluori-

dated dentifrices, and mouth rinses or high-dose fluoride gels

and varnishes. Regular fluoridation of restorative materials

is mainly performed by toothbrushing with fluoridated den-

tifrices or fluoride gels.Daily exposition of filling materials to fluoridated den-

tifrices has demonstrated a high rechargibility for glass-

ionomers [52,119,122,129], while the replenishment of resin-

based materialsseemsto be negligibly small [52,77,122]. Olsen

etal. [129] evaluated fluoride release of an aged resin-modified

glass-ionomer after daily exposure (30 min daily over 10 days)

to different toothpaste slurries. Application of fluoridated

(0.05%) and non-fluoridated dentifrices with pH 2.5, 5.7 and

8.3 increased the amount of fluoride release during the expo-

sure period, but was highest for the acidic slurry regardless

whether it was fluoridated or not. However, after the expo-

sure period fluoride levels in all groups, except the fluori-

dated and non-fluoridated dentifrices with pH 2.5, decreasedbelow baseline rates within 10 days [129]. Moreover, a constant

decrease of fluoride release is also reported during the period

of daily toothpaste exposure [52,118]. Attin et al. [52] found

that 5 min toothpaste slurry (1250ppm F and 5ml artificialsaliva) application also increases the fluoride re-release from

glass-ionomer specimens but not from compomers. Fluoride

re-release of glass-ionomers might also be increased when

application of the fluoridated dentifrice is performedby brush-

ing of samples instead of storage of the samples in dentifrice

slurries only [130].

In general, refluoridation seems to be more effective with

increasing concentration of the agent [117,131] and frequency

of application [122,128] as well as under acidic conditionsof the environment [52,118], e.g. in a simulated high caries

challenge situation. This was also shown for fluoridation of

restoratives with fluoride gels and solutions [19]. Daily immer-

sion in 250, 1000 and 2500ppm fluoride solution increased

the amount of leached fluoride from glass-ionomers from 1

to 215 ppm per day over the experimental period [19]. Refluo-

ridation of compomers and conventional and resin-modified

glass-ionomers was also more effective after application of

0.2% NaF solution than after treatment with 0.02 or 0.04% NaF

solution [33,132], but fluoride levels did not exceed 6.5 ppm

[33]. With regard to the kind of fluoride, 1.23% APF gels seem

to be more effective than neutral 1% NaF gel and 0.001%

CaF2 or 4% SnF2 agents [47,133,134]. After refluoridation with

7/28/2019 10.Wiegand, 2007

7/20

7/28/2019 10.Wiegand, 2007

8/20

350 d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 343362

phatase, peroxidase and catalase may be affected by fluoride

ions [154].

Although even low fluoride levels may reduce bacterial

growth, dental plaque composition and acid production in

vitro [156160], the clinical importance of the affection of

plaque metabolism by fluorides is still unclear [161,162]. Fluo-

ride concentrations needed for antimicrobial effects mostly

surpass the concentration needed to reduce the solubilityof apatite. In vitro, only small amounts of fluoride (approxi-

mately 0.030.08 ppm) in remineralizing solutions are neces-

sary to shift the equilibrium from demineralization to rem-

ineralization. Therefore, it is often considered that the antimi-

crobial effect of fluoride is less important when the fluoride

concentration required for inhibition of demineralization is

exceeded.

However, several clinical studies found that the fluoride

concentration of plaque on or adjacent to glass-ionomers

is increased and the proportion of mutans streptococci in

plaque is reduced [149,151,152,163165]. Fluoride levels of 14-

day-old plaque grown adjacent to glass-ionomers decreased

from 19,985ppm after 14 days to 5788ppm after 28 daysand 5019 ppm after 43 days, but was considerably higher

than fluoride concentration of plaque grown on composite

(about 200 ppm) [149]. Contradictory, Seppa et al. [148] found

no increased fluoride concentration of approximal plaque of

teeth close to glass-ionomer restorations either after two or

four weeks. In patients using fluoridated toothpastes, fluo-

ride levels detected in plaque adjacent to one-year-old resin-

modified glass-ionomer (6 nmol/mg), compomer (3 nmol/mg)

and resin composite (3.1nmol/mg) restorations were only

slightly increased compared to the fluoride content of enamel

plaque (1.2 nmol/mg) [166].

Even refluoridation of three-year-old glass-ionomers with

1.2% fluoride gel did not increase plaque fluoride concentra-tion significantly [149].

However, in a chemo-stat experiment it was shown that

fluoride can inhibit the growth of oral streptococci in vitro at

concentrations in the order of 0.160.31 mol/l [167]. This con-

centration is much higher as found in dental plaque adjacent

to fluorid-containing restoratives. Due to this fact, the results

of some in vivo investigations mostlyshowed that thefluoride

concentrations released from one- to three-year-old restora-

tives are not high enough to affect the metabolism of caries-

associated bacteria, e.g. mutans streptococci and lactobacilli

in dental plaque [150,166,168]. In contrast, studies investigat-

ing glass-ionomer restorationsup to one month after insertion

showed a correlation between fluoride release and reducedmutans streptococci counts in plaque [150,151,163165] or

saliva [39]. However, levels of mutans streptococci in plaque

from compositeor amalgam fillings were lower than in plaque

formed on glass-ionomers [150,163165].

The caries-preventive effect of resin-modified glass-

ionomers has also been related to decrease in microbial col-

onization of carious dentin. In vivo, a resin-modified glass-

ionomer restoration leads to a larger decrease in counts of

mutans streptococci and lactobacilli in remaining carious

dentin than amalgam [169,170]. In contrast, Weerheijm et al.

[171] found no differences in numbers of oral streptocci and

lactobacilliin dentinlesion two yearsafterinsertion of a glass-

ionomer or a resin-based sealant.

It has already been discussed that other components

simultaneously released from ionomeric-based (e.g. alu-

minium and zinc) or resin-based materials (monomers and

catalysts) may be involved in the antibacterial activity of the

materials [35,152,172].

In conclusion, fluoride is known to inhibit the biosyn-

thetic metabolism of bacteria, but these antimicrobial effects

in caries prevention are often regarded as little or of noimportance as compared to the direct interactions of fluo-

ride with the hard tissue during caries development and pro-

gression. There is still a lack in studies whether the antibac-

terial effects clinically contribute to the anticaries effect

of fluoride and whether fluoride leached from restoratives

into plaque or saliva may be relevant for these antibacterial

effects.

7. Fluoride uptake of adjacent toothstructure

For many years the cariostatic effect of fluoride was attributedto the incorporation of structurally bound fluoride in the

hydroxyapatite crystal lattice and the reduced solubility of the

so-formed fluoridated hydroxyapatite. However, recent obser-

vations have found that fluoride in the aqueous phase sur-

rounding the carbonated apatite crystals is much more effec-

tive in inhibiting demineralization than fluoride incorporated

into the crystals [4]. Fluoride may precipitate onto tooth sur-

faces as calcium fluoride-like layer, which serves as a reservoir

for fluoride when the pH drops [4]. This calcium fluoride-like

material, so-called KOH-soluble fluoride, facilitates the repre-

cipitation of minerals by forming fluoroapatite or fluorohy-

droxyapatite, thereby preventing further loss of mineral ions

[4,173]. Nevertheless, enamel resistance to lesion formationalso increased with increasing content of tooth-bound fluo-

ride [174].

Glass-ionomers and other fluoride-releasing restoratives

are reported to increase both the structurally bound and KOH-

soluble fluoride content of the adjacent dental hard tissues

[151,175182]. Fluoride uptake into dental hard tissues in the

absence of an acidic medium mainly occurs by slow diffu-

sion processes. Moreover, glass-ionomerscontaining bioactive

glass are shown to induce precipitation of calcium fluoride-

like compounds on dentin slabs, when immersed into simu-

lated body fluid [27].

Kawai et al. [175] investigated the amount of structurally

bound and KOH-soluble fluoride after fixation of fluoride-containing composite slabs onto enamel surfaces. Mean total

fluoride uptake at 10m depth amounted to 300600ppm and

decreased to approximately 200ppm at 30m depth. However,

amount of structurally bound and KOH-soluble fluoride at 10,

20and 30m depths was notsignificantly differentamongthe

different fluoridated composites [175]. In vivo, fluoride uptake

fromfluoridated composite slabs fixedto enamel surfacesalso

decreased only slightly from 785 to 590 ppm at levels from 2.5

to 50m depth [183].

The mean penetration depth of fluoride released from flu-

oridated composites into the enamel and dentin side walls of

class V restorations four weeks after insertion ranged from

19 to 47m [178]. Fluoride concentration at these cavity walls

7/28/2019 10.Wiegand, 2007

9/20

d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 343362 351

amounted to 42009400 ppm [178] which reflects the distinct

fluoride uptake.

For conventional and resin-modified glass-ionomers, flu-

oride uptake was also found to be highly significant in both

primary and permanent enamel [151,184]. Conventional glass-

ionomer cements seemed to be more effectively increasing

the content of fluoride in enamel and root surfaces than

metal-reinforced glass-ionomers due to a higher release offluoride [24,185]. In vitro, one month after application of glass-

ionomer-based restorations enamel fluoride uptake adjacent

to the restoration amounted to 24004100 ppm [181] and was

nearly the same after three and six months. In a distance of

1.57.5 mm to the margin of the restoration fluoride uptake by

more than 2000ppm was found [181].

Under in situ simulation of a high cariogenic challenge,

enamel fluoride uptake around glass-ionomers was twice

greater and mineral loss twice lower than in enamel restored

with non-fluoridating composites [151].

Enamel fluoride uptake in the vicinity of 1 or 5% SnF2silver amalgam restoration was found to be approximately

100200ppm after one month [182].Due to differences in microstructure and porosities of den-

tal hard tissues, the amount of fluoride uptake from restora-

tives and the depth of fluoride penetration are higher for both

dentin and cementum than for enamel [109,175,177,181,182].

Fluoride penetration fromdifferent restoratives intodentin

was highest for conventional glass-ionomers (300m, one

week after insertion) followed by resin-modified glass-

ionomers and composites [180]. Fluoride concentration of

dentin beneath a glass-ionomer cement filling might increase

to approximately 2000 ppm compared to the fluoride concen-

tration beneath a zinc phosphate cement filling [186]. Other

investigations found higher amounts of fluoride uptake for

fluoride-releasing resins (300012,000 ppm) [177,178] than forglass-ionomers (50006000 ppm) into side and axial walls of

dentin cavities [177]. One month after insertion of a glass-

ionomer restoration fluoride acquisition by cementumlocated

1.57.5 mm distant to the filling was about 14,00016,000ppm.

Reevaluation of fluoride uptake after three and six months

still revealed 60007000 and 50006000ppm, respectively [181].

After insertion of various fluoride-containing composites, the

concentration of total fluoride in cementum amounted to

2003500ppm at 10m depth and decreased to 1002500ppm

at 30m. Thereby, levels of bound fluoride uptake were

approximately 1002000ppm at 10m depth and501000ppm

at 30m depth [175].

An increase of fluoride concentrationin dental hard tissuesis also reportedfor SnF2 silver amalgam. Thereby, fluoride was

taken up to a greater extent from 5% SnF 2 than from 1% SnF2and was generally higher in dentin than in enamel [182].

As mentioned above, fluoride uptake from fluoride-

releasing restorations is higher in dentin and cementum than

in enamel, but is influenced by the interface between restora-

tion and tooth [180]. The presence of an intermediary micro-

gap or material layer between the restoration and the dental

hard tissues could restrict or promote the passage of fluoride.

Gapformation between the filling material and the cavity wall

will lead to a fluoride transport acrossthe fluid-filled gap. The-

oretically, a small gap withminimal fluidexchange will elevate

fluoride concentrationand create a greater diffusion potential.

Some of the fluoride will adsorb onto apatite crystallites and

become firmly bound. High concentrations of calcium, phos-

phate and fluoride at the interface may facilitate the precip-

itation of calcium fluoride-like compounds [187]. An infrared

spectroscopic analysis concluded that the interface between

glass-ionomers and dentin consisted of fluoridated carbona-

toapatite. The presence of this sparinglysoluble mineral at the

interface between the tooth and the restoration may providecaries resistance[188]. It wasdiscussed that theamount of flu-

oride released fromrestoratives and incorporated into enamel

is less important in lesion formation than the amount of flu-

oride released into the gap [66]. Extrapolation from in vitro

and in situ data indicated that a gap fluoride concentration

between 5 and 80 ppm might be the optimal range to prevent

caries formation [66,189]. Depending on the storage media,

both conventional and resin-modified glass-ionomers were

able to release fluoride in the required range (up to 100 ppm in

between 24 and 48 h after immersion). However, in the pres-

enceof a standardized interfacial gap,no preventive effect was

exerted in vivo from a glass-ionomer to protect the adjacent

enamel wall with respect to development of secondary caries[190].

With regard to fluoride released by restoratives which

are applied in a cavity it should be noted that acid etching

of dentin as performed in the total etching technique may

increase its permeability [191], and therefore also the depth

of fluoride uptake. Thereby, the preparation of self-etching

adhesives with pre-reacted glass-ionomer fillers increased

the release of fluoride from these experimental adhesives

[192]. Additionally, the application of hydrophilic primers may

improve the wetting of dentin andtherefore facilitate the pas-

sage of fluoride. In contrast, the hybrid layer formed after pre-

treatment of a cavity with an adhesive agent may reduce fluo-

ride diffusion. It shouldbe noted that a thick hybrid layer itselfmight act as acid-resistant layer hampering caries formation

[193]. These aspects should be taken into consideration when

anticaries activity of modern restoratives is estimated.

By summarizing these data, fluoride uptake of the adja-

cent dental hard tissueis higher in dentin andcementum than

in enamel, but is highly influenced by the interface between

restoration andtooth. Thereby, an intermediarymateriallayer,

such as an adhesivehybrid layer, may hamper fluoride uptake.

However, the amount of fluoride incorporated in dental hard

tissuesmight be of minor importance comparedto the fluoride

concentration in a fluid-filled microgap between the restora-

tionand the toothstructure. Thereby, severalrestorative mate-

rials might increase the fluoride concentration in the gap tothe required range between 5 and 80 ppm, which is estimated

to prevent caries.

8. Influence of fluoride-releasingrestoratives on caries development andprogression

8.1. Influence on demineralization of enamel adjacent

to fluoride-releasing restoratives

8.1.1. In vitro studies

In vitro, several fluoride-releasing restoratives have shown

to inhibit enamel and dentin demineralization produced by

7/28/2019 10.Wiegand, 2007

10/20

352 d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 343362

acidic gels or demineralizing buffer solutions. Thereby, inhi-

bition of enamel demineralization is located up to a distance

of 7 mm from the edge of the material (remote effect). When

compared with non-fluoride-releasing restorations, the place-

ment of glass-ionomers reduces mineral loss by almost 80%

at 0.22 mm distance from the restoration and by 37% 7 mm

distant from the restoration margin [194]. Glasspoole et al.

[195] examined the reductionin enamel demineralization pro-vided by fluoride-releasing glass-ionomers and composites.

Lesion areas were measured by polarized light microscopy

at distances from 100 to 800 m. At all distances, a signifi-

cant inhibition of enamel demineralization was seen for all

materials. Thereby, the degree of protection was highest in

the closest vicinity of the material, but lesion areas increased

with distance in an inverse relationship to the amount of

fluoride release [195]. These results were confirmed by micro-

radiographic assessment of artificial caries lesion depth and

mineral density of enamel adjacent to a conventional and a

resin-modified glass-ionomer. Forboth materials, lesion depth

increased and mineral density decreased with increasing dis-

tance (13 mm) from the restoration margin [196].As seen by polarized light microscopy, the placement of

conventional glass-ionomers results in a reduction of wall

lesion frequency and size of caries-like lesions in vitro. Reduc-

tion of enamel outer lesion size and depth ranged from 58 to

80% compared to the lesion size adjacent to non-fluoridated

filling materials [180,197199]. Wall lesion size and depth

were also decreased and amounted to approximately 30%

compared to the lesions adjacent to a non-fluoride-releasing

restorative [198]. For primary enamel samples it was shown

that placement of an amalgam-bonding resin with fluoride-

releasing capabilities provided a reduction of surface lesion

depth by 30% and a decrease in cavity wall lesion frequency

by 35% comparedto a conventionalamalgam restoration [200].Six to 10 weeks after insertion of different fluoride-

releasing materials, comparison of enamel surface and wall

lesion development and progression adjacent to the restora-

tion mostly revealed highest demineralization protection for

glass-ionomers (reduction of lesion size compared to non-

fluoridated control: 5880%), followed by resin-modified glass-

ionomers and compomers (reduction of lesion size compared

to non-fluoridated control: 3575%) and composites (reduc-

tion of lesion size comparedto non-fluoridated control: 940%)

[180,197199,201204].

The amount of fluoride in the restorative material seems

to influence the anticaries properties. In this sense, experi-

mental fluoride-releasing composites showed that wall lesiondevelopment and length of penetration of enamel deminer-

alization were more decreased adjacent to a resin containing

33% fluoride than for the composite containing 17% fluoride.

However, both experimental materials exhibited significantly

less demineralization of enamel surrounding the restoration

than a non-fluoridated composite and less or equal deminer-

alization than a fluoride-releasing silicate cement [205].

Other studies examined the remineralizing properties of

fluoride-releasing restoratives. The mean size reduction of

an artificial lesion adjacent to a fluoride-releasing composite

restoration amounted to 1227% after two weeks and 4080%

after three months compared to a non-fluoride-releasing

restorative [203].

8.1.2. In situ and in vivo studies

As shown in the above mentioned reports and investigations,

several in vitro studies found fluoride-releasing materials

effective in prevention of secondary caries. However, clinical

relevance of these artificial caries experiments is debatable.

Papagiannoulis et al. [190] evaluated the anticariogenicbehav-

ior of glass-ionomers and resin composite restorative materi-

als and found no correlation between in vivo andin vitro data.In vitro, glass-ionomer and fluoride-free composite restora-

tions applied in enamel cavities were stored in acidic gel for

four weeks to produce artificial caries-like lesions. For the in

vivo experiment, glass-ionomer and fluoride-free composite

restorations were inserted into premolars in a split-mouth

design. The premolars were extracted for orthodontic reasons

after six months. At regions without gaps, glass-ionomers

showed reduced lesion dimensions in vitro and no lesions

in vivo. At regions with gaps, no differences were found in

lesion depth between the tested materials in vitro, while in

vivo lesion dimensions were significantly greater for glass-

ionomers than for fluoride-free composites [190].

Currently, only few studies determined the demineraliza-tion behavior of enamel adjacent to fluoride-releasing restora-

tives in situ or in vivo [151,206209].

Kielbassa et al. [206,207] evaluated the effects of a con-

ventional and a resin-based glass-ionomer, different polyacid-

modified composites, an ion-releasing material and a compos-

ite on enamel lesion formationin situ. Thereby, intraoral appli-

ances were wornfor fourweeks without additional application

of topical fluorides. Only the ion-releasing material Ariston

leads to significantly lower lesion depth and mineral loss in

those areas of the developed caries lesions which were close

to the restoration. All other materials exhibited no preventive

effect on secondary caries formation [206,207].

As evaluated by microhardness measurement at variousdepths (10110m) and distances (130 and 230m) from

the edge of metallic restorations, fluoride-releasing resin-

modified or resin-based luting materials were not effective

in prevention of secondary caries of enamel and dentin in

situ [152]. In contrast, a fluoride-releasing glass-ionomer lut-

ing cement was able to reduce secondary caries development

in dentin but not in enamel [210]. The in situ simulation of a

highcariogenic challenge provoked significantlyhigher micro-

hardness values adjacent to a glass-ionomer cement than to

a non-fluoridated composite [151].

In a further in situ investigation, the effect of different

fluoride-containing composites (026 vol%fluoride)on enamel

demineralization around an artificial gap of 200m width was

quantified by micrographic measurements after one month.

At the gap margins,all fluoridated composites reducedenamel

demineralization (both lesion depth and mineral loss) signifi-

cantly with respect to the non-fluoridated control. At the outer

enamel surface next to the artificial gap, a beneficial effect of

fluoridation wasonly observed near to thecomposite with the

highest fluoride content [189]. It is noteworthy to mention that

fluoride concentration of the highly fluoridated experimental

composite was much higher than the content in commercially

available composites.

In conclusion, several in vitro studies found evidence for

an inhibition of enamel demineralization, while in situ and in

vivo studies found contradictory results, which do not allow

7/28/2019 10.Wiegand, 2007

11/20

d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 343362 353

for a final appraisal of the caries-inhibiting effects of fluoride-

releasing restoratives.

8.2. Influence on demineralization of dentin adjacent

to fluoride-releasing restoratives

8.2.1. In vitro studies

Several laboratory tests also investigated the ability of flu-oridated materials to prevent or inhibit demineralization of

adjacent dentin [180,211219].

Both conventional and resin-modified glass-ionomers as

well as compomers increased dentin resistance to cariogenic

or acidic challenges. Thereby, caries-like lesions in dentin

and cementum root surfaces adjacent to class V restora-

tions were reducedby 5463% (glass-ionomers), 2053% (resin-

modified glass-ionomers) or 1435% (compomers and giomer),

respectively, compared to non-fluoridated control materials

[211,212,217,220,221]. Also, fluoridated composites and amal-

gams reduced the depth of caries-like lesions adjacent to

restorations to 81 or 90.5%, respectively, compared to non-

fluoridated amalgams [217]. However, after immersion of rootdentin samples in a buffered demineralizing solution, an inhi-

bition zone adjacent to both conventional and resin-modified

glass-ionomer cements could be found which was less

frequently observed around a fluoride-releasing composite

[204].

Fluoride-releasing restoratives are also effective in preven-

tion of artificially created dentin wall lesions [180,212]. Size

of wall lesions adjacent to conventional or resin-modified

glass-ionomers was inhibited by 3040% compared to lesion

size adjacent to a non-fluoridated composite [180]. When

compared to unaltered materials, the incorporation of casein

phosphopeptideamorphous calcium phosphate or bioactive

glass into a glass-ionomer cement was associated with anincrease of fluoride release and an enhanced protection of the

adjacent dentin during acid challenge [27,28]. Also, the extent

of the cariostatic effect on root dentin provided by fluoride-

containing restoratives was evaluated by Knoop microhard-

ness measurement. While a fluoride-releasing composite and

a compomer exhibited no cariostatic effect, the extent of the

cariostatic effect was located up to 300m for the conven-

tional glass-ionomer and 150m for the resin-modified glass-

ionomer cement [222].

However, demineralization behavior at margins of fluoride-

releasing restorations might be influenced by topical fluo-

ride regimes. Glass-ionomers demonstrated significantly less

dentin demineralization than amalgam restorations when noexternal fluoride was applied or when the restorations were

either brushed with a fluoridated dentifrice twicedaily or were

exposed to a fluoride rinse. There was no significant difference

in dentin demineralization adjacent to the materials when

both a fluoride rinse and a fluoridated dentifrice were used

on a daily basis over 30 days [223].

Determination of lesion depth by confocal laser scan-

ning microscopy revealed differences in the caries-preventive

properties of fluoridated materials when used in chemical

or antimicrobial in vitro caries models [213]. Glass-ionomer

cement demonstrated anticarious properties for adjacent

dentin when exposed to a demineralizing solution (chemical

caries model). However, this was not true for glass-ionomer

and resin-modified glass-ionomer nor compomer and com-

posite restorations in a microbial caries model (inoculation

of the specimens to a solution containingStreptococcus mutans

and Lactobacillus casei) [213]. This findingwas confirmed in situ

when evaluating the remineralization of artificially deminer-

alized dentin beneath glass-ionomers, whendentin waseither

contaminated with bacteria or not [224]. One year after inser-

tion, nanohardness values of the bacteria-contaminated teethwere not different comparedto the nanohardness values three

days after insertion, but were significantly lower than in the

non-bacteria-contaminated dentin [224].

8.2.2. In situ studies

Currently, there is only one study available evaluating the

effects of fluoridated restoratives to dentin caries develop-

ment in situ [225]. Superficial caries-like lesions (25m depth

of demineralization) were submittedto severe plaque environ-

ment for three months in situ. Insertion of a glass-ionomer

restoration adjacent to the artificial demineralization zone

leads to a hypermineralization to an average depth of 125m.

Also, for deeper lesions (100 m) a hypermineralization of thedentin tissue up to a depth of 300 m could be observed. How-

ever, non-fluoridated amalgam or composite controls exhib-

ited either further demineralization or showed a large vari-

ety in the degree of demineralization or remineralization,

respectively. From these results the authors also concluded

that hypermineralization as promoted by the glass-ionomer

cement may increase the acid resistance by limiting the num-

ber of diffusion pathways for acids formed in plaque [225].

Even though in vitro studies found evidence for the caries-

inhibiting effect of fluoride-releasing restoratives on dentin,

the small amount of in situ data do not suffice for final con-

clusions.

8.3. Clinical studies evaluating secondary caries

adjacent to fluoride-releasing restoratives

Despite the cariostatic effects possibly achieved fromfluoride-

releasing materials, secondary caries is still one of the main

reasons for clinical failure of restorations (for review see

[226228]).

Unfortunately, only fewlongitudinal studies with an obser-

vation period of three and more years exist which evalu-

ate secondary caries adjacent to fluoride-releasing and non-

fluoride-releasing materials. To estimate the impact of flu-

oride release on secondary caries development, split-mouth

designed studies evaluating different materials in the samepatients seem to be more appropriate than studies dealing

with a single material in the respective patients. In split-

mouth designed studies, test and control material are sub-

jected to the same individual conditions and caries risk

parameters. With regard to secondary caries development,

however, these studies showed contradictory results.

Three-year success rate of class II restorations performed

with either a compomer (Compoglass) and a non-fluoridated

composite (TPH-Spectrum) [229] or a compomer (Dyract) and

a non-fluoridated amalgam (Tytin) [230] found no differences

between the materialsin relation to caries development in pri-

mary molars. Also, a three-year clinical evaluation of either a

compomer (Dyract), a composite (TPH-Spectrum) and a com-

7/28/2019 10.Wiegand, 2007

12/20

354 d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 343362

pomer/composite (sandwich-technique, Dyract layered with

TPH-Spectrum) [231] or a compomer/composite sandwich

restoration anda composite restoration [232] of class II cavities

found no differences in secondary caries development. These

results are also confirmed for class I compomer/composite

(sandwich) and composite restorations during an observation

period of six years [233].

Van Dijken [234] found no differences in secondarycaries development of class III cavities restored with a

polyacid-modified glass-ionomer (Dyract), a conventional

glass-ionomer (Fuji II LC) and a composite (Pekafill) in a three-

year observation period. Also, an intra-individually compari-

son of ceramic inlays luted with either a resin-modified glass-

ionomer cement (Fuji Plus) or a resin composite (Panavia)

revealed no significant differences in secondary caries in a

five-year clinical evaluation [235].

In contrast, clinical evaluation of paired compomer(Dyract)

and glass-ionomer (Chemfil Superior) classes I and II restora-

tions in primary molars revealed significantly better perfor-

mance with regard to caries development for Dyract than

for Chemfil Superior. Fifteen restorations failed during thefollow-up period of 42 months. Thereby, six glass-ionomer

restorationsbut none of the compomer restorations failed due

to recurrent caries [236]. Also, comparison of conventional

(Fuji II) and resin-modified glass-ionomer (Vitremer) class II

restorationsof primary molars exhibitedless secondary caries

at the margins of the resin-modified glass-ionomer (none of

53 restorations) than at themargins of the conventional glass-

ionomer (4 of 62 restorations) [237]. Three-year examination

of resin-modified glass-ionomer and amalgam class II restora-

tions of primary molars exhibitedalso better caries-preventive

properties for the resin-modified glass-ionomer. While clin-

ical evaluation found no differences between the materials,

polarizedlight microscopy of the exfoliated teeth revealed sig-nificantly lessenamel demineralization at restoration margins

of the resin-modified glass-ionomer than at the margins of

the amalgam restoration [238]. Six-year follow-up assessment

of class I restorations in permanent molars exhibited signif-

icantly more secondary caries for amalgam (10%) compared

to glass-ionomers (2%) [239]. In another five-year evaluation

of glass-ionomer (Ketac-Fil) and amalgam (Amalcap) restora-

tions in deciduous molars, the glass-ionomer had a lower

survival time and showed greater loss of anatomic form and

marginal integrity, but less recurrent caries compared to the

amalgam [240]. However, fluoridated amalgam used in class

I cavities of permanent molars exhibited less caries develop-

mentwithin fouryears comparedto non-fluoridated amalgam[241].

9. Influence on caries formation of teethlocated in interproximal contact tofluoride-releasing restoratives

9.1. In vitro and in situ studies

It is also discussed whether fluoride-releasing restoratives

might be effective in inhibition of incipient carious lesions

of neighboring teeth located in interproximal contact to the

restoration.

In vitro andin situ investigations found that glass-ionomer

and resin-modified glass-ionomer restorations in direct con-

tact to adjacent teeth prevent demineralization compared to

non-fluoridated amalgam and composite [209,242]. However,

additional application of topical fluoride (fluoridated denti-

frice) significantly increased remineralization and decreased

demineralization,respectively, in all groups independent from

the material [209,242]. This was also confirmed in anotherin situ investigation, where glass-ionomers showed some

slight caries-preventive effects compared to a fluoridated and

a non-fluoridated composite when subjects performed oral

hygiene without topical fluorides. The regular application of

fluoridated toothpaste was, however, effective in prevention

of secondary caries in all experimental groups [243]. In vitro,

it could also be shown that placement of a resin-modified

glass-ionomer exhibited nearly the same remineralization

effects on adjacent caries as toothpaste application twice

daily, but both fluoride regimes were less effective than the

daily use of a fluoridated rinse [244]. A one-year evaluation

of glass-ionomer, resin-modified glass-ionomer and resin

composite class V restoration in xerostomic head and neckradiation patients found differences depending on the fre-

quency of topical fluoridation. No recurrent caries was found

in patients using fluoride gels at regular intervals. However, in

patients using fluoride gels at irregular intervals, less enamel

caries was evident for glass-ionomer and resin-modified

glass-ionomer restorations than for composite fillings

[245].

Therefore, it is assumed that topical fluoridation over-

whelmingly increases the ability of the fluoridated restora-

tives to inhibit demineralization and promote remineraliza-

tion on the adjacent interproximal incipient caries lesion. On

the other hand, it might be postulated that theuse of fluoride-

releasing restoratives does provide additional protection forpatients who might not strictly follow the recommended pro-

phylactic measures.

The effect of a glass-ionomer, a resin-modified glass-

ionomer, a compomer and a non-fluoridated composite on

sound enamel of approximal teeth without additional topical

fluoride treatment was also evaluated in situ. Specimens were

worn for 70 days under cariogenic conditions. Enamel micro-

hardness assessment was located at 0, 0.4, 0.8 and 1.2mm

distances from the contact point. Microhardness alteration

wasgenerally lowest for the resin-modified glass-ionomer, fol-

lowed by the conventional glass-ionomer and the compomer.

The resin-modified glass-ionomer exhibited none and glass-

ionomers and compomers only slight alterations, while thenon-fluoridated composite showed distinct formation of sub-

surface enamel lesions [208]. Also, remineralization of artifi-

cial caries-like lesions adjacent interproximally to teeth with

class II restorations was higher in metal-reinforced glass-

ionomers and amalgam than in glass-ionomer/resin compos-

ite restorations [246].

9.2. Clinical studies

Currently, onlyfew clinical studiesexist concerning the effects

of fluoride-releasing restoratives at the caries development of

proximal tooth surfaces.

7/28/2019 10.Wiegand, 2007

13/20

d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 343362 355

In a three-year study in split-mouth design, caries develop-

ment on tooth surfaces adjacent to class II amalgam (Disper-

salloy) and glass-ionomer tunnel restorations was assessed.

While the materials exhibited no differences with regard to

secondary caries development at the restoration margins, pri-

mary caries was significantly reduced on tooth surfaces adja-

cent to the glass-ionomer restorations as compared to sur-

faces in contact to amalgam restorations [247]. A seven-yearstudy on three resin-modified glass-ionomer cements (Fuji II

LC, Photac-Fil and Vitremer) and a compomer (Dyract) showed

that the restorative material and cavity conditioning influ-

enced the survival of the restoration but not the progression

of caries on adjacent surfaces [248].

In summary, clinical studies exhibited inconsistent results

concerning the prevention of secondary caries by fluoride-

releasing restoratives. Despite the high release of fluoride ions

in some studies, secondary caries has been found to be the

main reason for the clinical failure of glass-ionomer restora-

tions [249,250]. Furthermore, glass-ionomer cements are not

considered as having adequate mechanical strength for gen-

eral use as definitive restorations in stress-bearing posteriorteeth (for review see [251]). Thereby, the annual failure rate

of glass-ionomers (7.2%) is distinctly higher as compared to

direct composite (2.2%), compomer (1.1%) or amalgam (3.0%)

restorations [251]. In contrast to glass-ionomers, compomer

and composite restorations exhibit a good clinical perfor-

mance over time concerning marginal integrity and discol-

oration, surface texture, anatomic form and occlusal wear.

However, although compomers and some composites are able

to release fluoride in a range that might have cariostatic effi-

cacy, it is still unproven whether their good clinical perfor-

mance is attributed to their ability to release fluoride. There-

fore, further investigations are necessary to determine the

impact of fluoride-releasing compomer and composite mate-rials on secondary caries formation. Furthermore, the devel-

opment of restorative materials with excellent mechanical

properties and a constant release of high amounts of fluoride

seem recommendable.

10. Conclusion

There is a continuum of restorative materials that range from

initially high fluoride release (conventional glass-ionomer

and resin-modified glass-ionomer) to intermediate fluoride

release (compomer) to low fluoride release (fluoride-releasing

composite and fluoride-releasing amalgam) to no fluoriderelease (non-fluoridated composite resins and amalgam)

[10,11,15,55,59,252,253]. However, the potential to release flu-

oride not only varies between different restorative materi-

als, but also within different brands. Optimal fluoride release

(short- and long-term release) from a restorative is related to

their matrices, setting mechanisms and fluoride content and

depends on several environmental conditions. Thereby, flu-

oride release is substantial only in the period immediately

following placement of the fresh material. However, it is not

evident whether initial burst or long-term release may be

clinically more important to prevent caries as certain rem-

ineralizing mechanisms need rather low but constantly pro-

vided quantities of fluoride. Nevertheless, fluoride-releasing

materials may act as a reservoir for fluorides from topical flu-

oridation and may lead to an elevation of the fluoride level

in plaque or saliva in the immediate vicinity of the restora-

tive. Despite the cariostatic effects achieved from an increase

of fluoride content in saliva, plaque and dental hard tissues,

clinical studies exhibited conflicting data as to whether or not

these materialssufficientlyprevent or inhibit secondary caries

compared to non-fluoridated restoratives. Therefore, furtherclinical studies, preferably in split-mouth design, are needed

to evaluate the impact of fluoride-releasing restoratives on

secondary caries development and progression especially in

patient groups that have limited access to or low compliance

with prophylactic measures.

Acknowledgement

The study was supported by a grant of the DENTSPLY DeTrey

GmbH.

r e f e r ence s

[1] Fejerskov O, Clarkson BH. Dynamics of caries lesionformation. In: Fejerskov O, Ekstrand J, Burt BA, editors.Fluoride in dentistry. Copenhagen: Munksgaard; 1996. p.187213.

[2] Rlla G, Ekstrand J. Fluoride in oral fluids and dental plaque.In: Fejerskov O, Ekstrand J, Burt BA, editors. Fluoride indentistry. Copenhagen: Munksgaard; 1996. p. 21529.

[3] Hamilton IR, Bowden GHW. Fluoride effects on oralbacteria. In: Fejerskov O, Ekstrand J, Burt BA, editors.Fluoride in dentistry. Copenhagen: Munksgaard; 1996. p.

23051.[4] ten Cate JM, Featherstone JDM. Physicochemical aspects of

fluorideenamel interactions. In: Fejerskov O, Ekstrand J,Burt BA, editors. Fluoride in dentistry. Copenhagen:Munksgaard; 1996. p. 25272.

[5] Verbeeck RM, De Maeyer EA, Marks LA, De Moor RJ, DeWitte AM, Trimpeneers LM. Fluoride release process of(resin-modified) glass-ionomer cements versus(polyacid-modified) composite resins. Biomaterials1998;19:50919.

[6] Lee SY, Dong DR, Huang HM, Shih YH. Fluoride iondiffusion from a glass-ionomer cement. J Oral Rehabil2000;27:57686.

[7] Tay WM, Braden M. Fluoride ion diffusion frompolyalkenoate (glass-ionomer) cements. Biomaterials

1988;9:4546.[8] Williams JA, Billington RW, Pearson GJ. A long term study of

fluoride release from metal-containing conventional andresin-modified glass-ionomer cements. J Oral Rehabil2001;28:417.

[9] Dhondt CL, De Maeyer EA, Verbeeck RM. Fluoride releasefrom glass ionomer activated with fluoride solutions. JDent Res 2001;80:14026.

[10] Xu X, Burgess JO. Compressive strength, fluoride releaseand recharge of fluoride-releasing materials. Biomaterials2003;24:245161.

[11] Karantakis P, Helvatjoglou-Antoniades M,Theodoridou-Pahini S, Papadogiannis Y. Fluoride releasefrom three glass ionomers, a compomer, and a compositeresin in water, artificial saliva, and lactic acid. Oper Dent

2000;25:205.

7/28/2019 10.Wiegand, 2007

14/20

356 d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 343362

[12] Bell A, Creanor SL, Foye RH, Saunders WP. The effect ofsaliva on fluoride release by a glass-ionomer fillingmaterial. J Oral Rehabil 1999;26:40712.

[13] Horsted-Bindslev P, Larsen MJ. Release of fluoride fromconventional and metal-reinforced glass-ionomer cements.Scand J Dent Res 1990;98:4515.

[14] Creanor SL, Carruthers LM, Saunders WP, Strang R, FoyeRH. Fluoride uptake and release characteristics of glass

ionomer cements. Caries Res 1994;28:3228.[15] de Araujo FB, Garcia-Godoy F, Cury JA, Conceicao EN.

Fluoride release from fluoride-containing materials. OperDent 1996;21:18590.

[16] Attar N, Turgut MD. Fluoride release and uptake capacitiesof fluoride-releasing restorative materials. Oper Dent2003;28:395402.

[17] Yap AU, Tham SY, Zhu LY, Lee HK. Short-term fluoriderelease from various aesthetic restorative materials. OperDent 2002;27:25965.

[18] Attar N, Onen A. Fluoride release and uptakecharacteristics of aesthetic restorative materials. J OralRehabil 2002;29:7918.

[19] Creanor SL, Saunders WP, Carruthers LM, Strang R, FoyeRH. Effect of extrinsic fluoride concentration on the uptake

and release of fluoride from two glass ionomer cements.Caries Res 1995;29:4246.

[20] Olsen BT, Garcia-Godoy F, Marshall TD, Barnwell GM.Fluoride release from glass ionomer-lined amalgamrestorations. Am J Dent 1989;2:8991.

[21] el Mallakh BF, Sarkar NK. Fluoride release fromglass-ionomer cements in de-ionized water and artificialsaliva. Dent Mater 1990;6:11822.

[22] De Moor RJ, Verbeeck RM, De Maeyer EA. Fluoride releaseprofiles of restorative glass ionomer formulations. DentMater 1996;12:8895.

[23] Forsten L. Short- and long-term fluoride release from glassionomers and other fluoride-containing filling materials invitro. Scand J Dent Res 1990;98:17985.

[24] Swift Jr EJ. In vitro caries-inhibitory properties of a silvercermet. J Dent Res 1989;68:108893.

[25] Williams JA, Billington RW, Pearson G. Silver and fluorideion release from metal-reinforced glass-ionomer fillingmaterials. J Oral Rehabil 1997;24:36975.

[26] DeSchepper EJ, Berr III EA, Cailleteau JG, Tate WH. Acomparative study of fluoride release from glass-ionomercements. Quintessence Int 1991;22:2159.

[27] Yli-Urpo H, Vallittu PK, Narhi TO, Forsback AP, Vakiparta M.Release of silica, calcium, phosphorus, and fluoride fromglass ionomer cement containing bioactive glass. JBiomater Appl 2004;19:520.

[28] Mazzaoui SA, Burrow MF, Tyas MJ, Dashper SG, Eakins D,Reynolds EC. Incorporation of caseinphosphopeptideamorphous calcium phosphate into aglass-ionomer cement. J Dent Res 2003;82:9148.

[29] Vermeersch G, Leloup G, Vreven J. Fluoride release fromglass-ionomer cements, compomers and resin composites.

J Oral Rehabil 2001;28:2632.[30] Mitra SB. In vitro fluoride release from a light-cured

glass-ionomer liner/base. J Dent Res 1991;70:758.

[31] Guida A, Hill RG, Towler MR, Eramo S. Fluoride release frommodel glass ionomer cements. J Mater Sci Mater Med2002;13:6459.

[32] Williams JA, Billington RW, Pearson GJ. The influence ofsample dimensions on fluoride ion release from a glassionomer restorative cement. Biomaterials 1999;20:132737.

[33] Dionysopoulos P, Kotsanos N, Pataridou A. Fluoride releaseand uptake by four new fluoride releasing restorativematerials. J Oral Rehabil 2003;30:86672.

[34] Strickland S, Retief DH, Russell CM. Shear bond strengthsto dentin and fluoride release from fluoride-containingliners. Am J Dent 1990;3:25963.

[35] Hayacibara MF, Ambrozano GM, Cury JA. Simultaneousrelease of fluoride and aluminum from dental materials invarious immersion media. Oper Dent 2004;29:1622.

[36] Perrin C, Persin M, Sarrazin J. A comparison of fluoride

release from four glass-ionomer cements. Quintessence Int1994;25:6038.

[37] Preston AJ, Mair LH, Agalamanyi EA, Higham SM. Fluoriderelease from aesthetic dental materials. J Oral Rehabil1999;26:1239.

[38] Asmussen E, Peutzfeldt A. Long-term fluoride release froma glass ionomer cement, a compomer, and fromexperimental resin composites. Acta Odontol Scand2002;60:937.

[39] Koch G, Hatibovic-Kofman S. Glass ionomer cements as afluoride release system in vivo. Swed Dent J 1990;14:26773.

[40] Hatibovic-Kofman S, Koch G. Fluoride release from glassionomer cement in vivo and in vitro. Swed Dent J1991;15:2538.

[41] Robertello FJ, Coffey JP, Lynde TA, King P. Fluoride release ofglass ionomer-based luting cements in vitro. J ProsthetDent 1999;82:1726.

[42] Musa A, Pearson GJ, Gelbier M. In vitro investigation offluoride ion release from four resin-modified glasspolyalkenoate cements. Biomaterials 1996;17:101923.

[43] Momoi Y, McCabe JF. Fluoride release from light-activatedglass ionomer restorative cements. Dent Mater1993;9:1514.

[44] Tjandrawinata R, Irie M, Suzuki K. Marginal gap formationand fluoride release of resin-modified glass-ionomercement: effect of silanized spherical silica filler addition.Dent Mater J 2004;23:30513.

[45] Forsten L. Fluoride release of glass ionomers. J Esthet Dent1994;6:21622.

[46] Grobler SR, Rossouw RJ, Wyk Kotze TJ. A comparison offluoride release from various dental materials. J Dent1998;26:25965.

[47] Gao W, Smales RJ, Gale MS. Fluoride release/uptake fromnewer glass-ionomer cements used with the ARTapproach. Am J Dent 2000;13:2014.

[48] Yip HK, Smales RJ. Fluoride release from apolyacid-modified resin composite and 3 resin-modifiedglass-ionomer materials. Quintessence Int 2000;31:2616.

[49] Yip HK, Smales RJ. Fluoride release and uptake by agedresin-modified glass ionomers and a polyacid-modifiedresin composite. Int Dent J 1999;49:21725.

[50] Forsten L. Fluoride release and uptake by glass-ionomersand related materials and its clinical effect. Biomaterials1998;19:5038.

[51] Shaw AJ, Carrick T, McCabe JF. Fluoride release fromglass-ionomer and compomer restorative materials:6-month data. J Dent 1998;26:3559.

[52] Attin T, Buchalla W, Siewert C, Hellwig E. Fluoriderelease/uptake of polyacid-modified resin composites(compomers) in neutral and acidic buffer solutions. J OralRehabil 1999;26:38893.

[53] Marks LA, Verbeeck RM, De Maeyer EA, Martens LC. Effectof a neutral citrate solution on the fluoride release ofresin-modified glass ionomer and polyacid-modifiedcomposite resin cements. Biomaterials 2000;21:20116.

[54] Marks LA, Verbeeck RM, De Maeyer EA, Martens LC. Effectof maturation on the fluoride release of resin-modified

7/28/2019 10.Wiegand, 2007

15/20

d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 343362 357

glass ionomer and polyacid-modified composite resincements. Biomaterials 2000;21:13738.

[55] Savarino L, Cervellati M, Stea S, Cavedagna D, Donati ME,Pizzoferrato A, et al. In vitro investigation of aluminum andfluoride release from compomers, conventional andresin-modified glass-ionomer cements: a standardizedapproach. J Biomater Sci Polym Ed 2000;11:289300.

[56] Aboush YE, Torabzadeh H. Fluoride release from

tooth-colored restorative materials: a 12-month report. JCan Dent Assoc 1998;64:5614, 568.

[57] Attin T, Kielbassa AM, Plogmann S, Hellwig E. Fluoriderelease from compomers in the acidic and neutralenvironment. Dtsch Zahnarztl Z 1996;51:6758.

[58] Sales D, Sae-Lee D, Matsuya S, Ana ID. Short-term fluorideand cations release from polyacid-modified composites ina distilled water, and an acidic lactate buffer. Biomaterials2003;24:168796.

[59] Yap AU, Khor E, Foo SH. Fluoride release and antibacterialproperties of new-generation tooth-colored restoratives.Oper Dent 1999;24:297305.

[60] Attin T, Buchalla W, Ameling K, Hellwig E. Effec